1. Field of the Invention
This invention relates to a particle analyzing device such as a flow cytometer for applying a light to flowing particles to be examined and detecting the optical reaction thereof, thereby accomplishing measurement of the particles to be examined.
2. Related Background Art
The flow cytometer is a device for applying for example, a laser beam to a cell floating solution flowing at a high speed, i.e., sample fluid, detecting the photoelectric signal by the scattered light or fluorescence thereof and making clear the nature and structure of cells, and is used in the fields of cytochemistry, immunology, hematology, oncology, genetics, etc.
In the conventional particle measuring device used in such flow cytometer or the like, sample fluid flows through the flow-through portion of the central portion of a flow cell having, for example, a minute square cross-section of 200 .mu.m.times.200 .mu.m while being wrapped in sheath liquid. An irradiating light such as a laser beam is applied to minute particles to be examined such as blood cells in the sample fluid passing one after another at a high speed, and forward scattered light, sideways scattered light, fluorescence or transmitted light produced as a result is measured, whereby measured values of several kinds of parameters are obtained with respect to several tens of thousand to several hundreds of thousands of particles to be examined. These numerous measured data are represented in the form of a histogram or a cytogram and subjected to statistical processing, whereby, analysis of the particles to be examined is effected and for example, the discrimination between the kinds of particles and the tendency of the natures thereof can be grasped.
Heretofore, design has been made such that particles to be examined pass through a light beam fixed and applied at a position to be examined, but usually a laser beam having a Gaussian strength distribution is used as an irradiating light source and therefore, the fixed light beam does not have a uniform strength distribution. Consequently, the particles to be examined have not always passed through the peak position of the Gaussian strength distribution due to the drift thereof into a direction orthogonal to the flow of the particles to be examined in the sample stream caused by various unstable factors of the device, or the drift thereof into a direction orthogonal to the flow caused by the disturbance of the sample stream itself, but light energy applied to each particle to be examined has differed. This has led to the problem that fluctuation or irregularity of measured values occurs to reduce the accuracy of analysis.
Also, discretely from the above-described flow cytometer, devices which can obtain two-dimensional information of individual particles to be examined are described in U.S. Pat. No. 3,918,812 and Japanese Laid-Open Patent Application No. 62-76462. In these devices, a beam spot smaller than the particles to be examined is continuously optically scanned at a high speed in a direction intersecting the flow of the particles to be examined, and the particles to be examined are substantially two-dimensionally scanned, whereby two-dimensional image information is obtained.
In these devices, however, a great deal of data storage memory is necessary per particle and this is not suitable for a flow cytometer for statistically effecting analysis, in respect of cost and processing speed.